<template>
  <span class="num" >
    {{ value }}
  </span>
</template>
<script lang="ts">
import {ref, defineComponent, watch, computed, watchEffect, onMounted, unref  } from 'vue'


const props = {
  startVal: { type: Number, default: 0 },
  endVal: { type: Number, default: 2021 },
  duration: { type: Number, default: 1500 },
  autoplay: { type: Boolean, default: true },
  decimals: {
    type: Number,
    default: 0,
    validator(value: number) {
      return value >= 0
    }
  },
  prefix: { type: String, default: '' },
  suffix: { type: String, default: '' },
  separator: { type: String, default: ',' },
  decimal: { type: String, default: '.' },
  /**
   * font color
   */
  color: {
		type: String,
		default: '#161840'
	},
	fontWeight: {
		type: String,
		default: 'bold'
	},
	fontSize: {
		type: String,
		default: '18px'
	},
  /**
   * Turn on digital animation
   */
  useEasing: { type: Boolean, default: true },
  /**
   * Digital animation
   */
  transition: { type: String, default: 'linear' }
}

export default defineComponent({
  name: 'CountTo',
  props,
  emits: ['onStarted', 'onFinished'],
  setup(props, { emit }) {
    function is(val: unknown, type: string) {
      return toString.call(val) === `[object ${type}]`
    }
    function isNumber(val: unknown): val is number {
      return is(val, 'Number')
    }
		function useTransition(source, options = {}) {
			const { disabled = ref(false), duration = 1500, onFinished, onStarted } = options
			const outputValue = ref(source.value)

			watch(source, (newValue) => {
				if (!disabled.value) {
					// 开始动画时调用 onStarted 回调
					onStarted && onStarted()

					// 创建过渡动画效果
					let startTime = Date.now()
					let initialValue = outputValue.value

					const step = () => {
						let elapsed = Date.now() - startTime
						if (elapsed < duration) {
							// 计算插值，根据缓动公式或线性公式平滑过渡
							outputValue.value = initialValue + (newValue - initialValue) * (elapsed / duration)
							requestAnimationFrame(step)  // 持续执行动画
						} else {
							// 动画结束，确保最终值是目标值
							outputValue.value = newValue
							// 动画结束时调用 onFinished 回调
							onFinished && onFinished()
						}
					}

					step()
				} else {
					outputValue.value = newValue
				}
			})

			return outputValue
		}



    const source = ref(props.startVal)
    const disabled = ref(false)




    let outputValue = useTransition(source)
    const value = computed(() => formatNumber(unref(outputValue)))

    /**
     * watchEffect 也是一个帧听器，是一个副作用函数。 它会监听引用数据类型的所有属性，不需要具体到某个属性，一旦运行就会立即监听
     * watchEffect 在响应数据初始化时就会立即执行回调函数。
     */
    watchEffect(() => {
      source.value = props.startVal
    })

    /**
     * watch 还可以监听数组，前提是这个数组内部含有响应式数据
     * watch 在响应数据初始化时是不会执行回调函数的
     */
    watch([() => props.startVal, () => props.endVal], () => {
      if (props.autoplay) {
        start()
      }
    })

    onMounted(() => {
      props.autoplay && start()
    })

    function start() {
      run()
      source.value = props.endVal
    }

    function reset() {
      source.value = props.startVal
      run()
    }

    function run() {
      outputValue = useTransition(source, {
        disabled,
        duration: props.duration,
        onFinished: () => emit('onFinished'),
        onStarted: () => emit('onStarted')
      })
    }

    /**
     * 将数字转化为千位分隔符的形式
     * @param num
     */
    function formatNumber(num: number | string) {
      if (!num && num !== 0) {
        return ''
      }
      const { decimals, decimal, separator, suffix, prefix } = props

      num = Number(num).toFixed(decimals)
      num += ''

      const x = num.split('.')
      let x1 = x[0]
      const x2 = x.length > 1 ? decimal + x[1] : ''

      const rgx = /(\d+)(\d{3})/
      if (separator && !isNumber(separator)) {
        while (rgx.test(x1)) {
          x1 = x1.replace(rgx, '$1' + separator + '$2')
        }
      }
      return prefix + x1 + x2 + suffix
    }

    return { value, start, reset }
  }
})
</script>

